Sibogasyrinx filosa Ardovini, 2021

Kantor, Yuri I. & Puillandre, Nicolas, 2021, Rare, deep-water and similar: revision of Sibogasyrinx (Conoidea: Cochlespiridae), European Journal of Taxonomy 773, pp. 19-60 : 41-43

Sibogasyrinx filosa Ardovini, 2021 (= PSH 6)

Figs 8C , 9A–H

Sibogasyrinx filosus Ardovini, 2021: 5–6 , textfigs (erroneous gender agreement of specific epithet).

Material examined

Holotype PAPUA NEW GUINEA • lv; NE of Bougainville I.; 04°30′ S, 157°20′ E; depth 1100–1200 m; MNHN-IM-2000-37629 (originally R. Ardovini collection).

Paratype PAPUA NEW GUINEA • 1 lv; same collection data as for holotype; R. Ardovini collection .

Other material (all sequenced)

PAPUA NEW GUINEA • 1 lv; New Ireland; 02°33′ S, 150°45′ E; depth 150–170 m; KAVIENG 2014, stn DW4500; MNHN-IM-2013-59044 .

SOLOMON ISLANDS • 1 lv; off Choiseul I. , Papua New Guinea Exclusive Economic Zone ; 06°37′ S, 156°13′ E, depth 508–522 m; SALOMON 2, stn CP2227; MNHN-IM-2007-42498 • 1 lv; Guadalcanal I.; 09°19′ S, 160°06′ E; depth 416–425 m; SALOMONBOA 3, stn CP2767; MNHN-IM-2009-16831 .

Description

MEASUREMENTS. Largest available specimen (MNHN-IM-2007-42498): SL 49.9 mm, AL (with canal) 28 mm, AL (without canal) 16.7 mm, SW 13.5 mm. Holotype has SL 52 mm.

SHELL. Moderately thick, strong except for fragile and often partially broken outer aperture lip, narrowly fusiform, with high spire and long, narrow, straight siphonal canal. Protoconch small, globose, of just over 1.5 strongly convex, microshagreened whorls (MNHN-IM-2009-16831). Protoconch/teleoconch transition indistinct, marked by appearance of shoulder carina. Protoconch diameter 0.89 mm, height 0.72 mm. Spire whorls strongly angled at shoulder, last whorl with more rounded shoulder. Total teleoconch whorls just under 9 in largest specimen. Suture shallowly impressed on last whorl and rather deep on spire ones, subsutural ramp moderately broad, strongly concave. Subsutural region with a row of distinct narrow axial ribs, confluent with growth lines and forming small nodules at intersections with spiral cords, absent on most of first teleoconch whorl, about 20 on second–third whorls, about 35 on penultimate and 45 on last whorl. Subsutural ramp with spiral cords, first visible on second whorl and distinct on fourth whorl. Last, penultimate and antepenultimate whorls with 4–5 distinct cords on subsutural ramp, their intervals equal to width of cords, followed below shoulder by 5–7 more narrow, closely spaced cords. Shoulder with row of pronounced rounded nodules, more distinct on upper teleoconch whorls and absent on last whorl, 15–17 on penultimate and antepenultimate whorls. Spiral sculpture in addition to cords on subsutural ramp of distinct narrow cords, covering entire shell surface, including shoulder nodules. On last whorl about 45 cords below shoulder, 25 of which on canal. Cords weakly rounded or flat on top, their intervals mostly narrower than cords themselves, rarely equal to or even slightly wider than cords. Shell base gradually narrowing towards long, narrow, almost straight siphonal canal. Aperture narrow, constricted posteriorly, with very narrow and thin parietal callus, outer lip with rounded angle at shoulder, weakly convex below shoulder, weakly concave at transition to canal. Anal sinus moderately deep, subsutural, broadly arcuate, confluent with large forward extension of outer lip. Shell light orange with lighter middle part of last whorl, in sequenced specimens off-white, with very light yellowish subsutural ramp and irregular darker blotches on subsutural ramp. Protoconch light tan.

ANATOMY (n = 1; MNHN-IM-2009-16831). Head with moderately long, conical tentacles, rounded on tips and with closely spaced bases, large eyes situated on small lobes at tentacle base. Proboscis conical, moderately long, with broad base, rapidly narrowing towards tip. Proboscis retractors not defined, entire posterior part of very thin proboscis sheath base weakly muscular. Buccal mass very large and broad, posterior to proboscis base, constituting about half of proboscis length, oesophagus forming a very short loop before nerve ring. Radular sac with small odontophore, opening dorso-laterally at right side of buccal mass. Venom gland thick, moderately long and convoluted, opening into oesophagus within nerve ring. Muscular bulb moderately large, elongated and folded in posterior part. Salivary glands fused, relatively large, of irregular shape, acinous. Small ovate accessory salivary gland situated dorsally at nerve ring.

RADULA (n = 1; MNHN-IM-2009-16831) ( Fig. 8C ). Relatively short, consisting of 41 rows of teeth, 15 nascent. Radula length 1.55 mm (12% of AL without canal), width up to 225 μm (1.8% of AL without canal). Central tooth with subrectangular basal plate, having distinct borders and moderately long cusp. Anterior margin overlapped by preceding row, posterior margin evenly and weakly rounded. Marginal teeth flat when formed, becoming trough-shaped with weakly thickened edges during maturation, folded longitudinally when fully formed, with both margins overlapping at tooth tip. Resulting folded tooth moderately broad, with sharp pointed tip, anterior edge with a narrow slit between folded tooth margins.

Remarks

Our specimens are very similar to the holotype and paratype (except lighter shells) and were collected close to the type locality. Our specimens were collected at much shallower depths (150–508 m) as compared to the holotype and paratype (1100 m). Nevertheless, the strong similarity of the shell shape and sculpture, especially obvious when comparing the holotype with sequenced specimen of the same size ( Fig. 9A–B and C–D ) suggests the conspecifity of our and the type specimens. Ardovini (2021) himself considered the specimen MNHN-IM-2007-42498 as belonging to his newly described species based on the photograph on the MNHN website. Smaller specimens (SL 34.4 and 29.9 mm) retain smooth, flaking, yellowish periostracum, better preserved in interspaces between cords.

This species is most similar to Sibogasyrinx subula sp. nov., but differs in having more strongly developed spiral cords on the subsutural ramp, a relatively narrower ramp resulting in a higher shoulder position on the spire whorls, a different radula and the presence of eyes. In shell outline the new species resembles some species of Leucosyrinx , particularly Leucosyrinx sp. A ( Fig. 13H ), but the shell is broader with more numerous nodules on the shoulder. Compared to Leucosyrinx sp. F ( Fig. 13K ), the shell of S. filosa is larger, broader and has a coarser sculpture.

Distribution

This species is found off the Solomon Islands Archipelago and New Ireland, at a broad depth range of 150–1100 m.

Figures

Fig. 8. Radulae of species of Sibogasyrinx Powell, 1969. A–B. Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018, MNHN-IM-2009-16995 (shell seen on Fig. 7C). A. Part of radula with fully formed marginal teeth; white hollow arrow indicates overlapping edges of the tooth at its tip. B. Part of radula showing transition between unfolded (white arrow) and completely longitudinally folded (black arrow) marginal teeth (ae = anterior tooth edge; pe = posterior tooth edge). C. Sibogasyrinx filosa Ardovini, 2021, Solomon Islands, MNHN-IM-2009-16831 (shell seen Fig. 9E–F). D. Sibogasyrinx lolae sp. nov., MNHN-IM-2009-29311. E. Sibogasyrinx maximei sp. nov., holotype, MNHN-IM-2013-45883, anterior end of radula. F. Sibogasyrinx pagodiformis sp. nov., MNHN-IM-2009-11327.

Fig. 9. A–H. Sibogasyrinx filosa Ardovini, 2021. A–B. Holotype, Solomon Islands (MNHN- IM-2000-37629), SL 52 mm. C–D. Solomon Islands, MNHN-IM-2007-42498, SL 49.9 mm. E–F. Solomon Islands, MNHN-IM-2009-16831, SL 34.4 mm (radula seen on Fig. 8C). G–H. Papua New Guinea, MNHN-IM-2013-59044, SL 29.9 mm. I–Q. Sibogasyrinx lolae sp. nov. I–J. Solomon Islands, holotype, MNHN-IM-42537, SL 37.3 mm. K–L. New Caledonia, MNHN-IM-2009-29230, SL 43.1 mm. M–N. New Caledonia, MNHN-IM-2009-29311, SL 29.1 mm. O–Q. New Caledonia, MNHN-IM-2013-48156, SL 17.1 mm (O at the same scale as the other specimens, P–Q enlarged). All shells (except P–Q) to same scale.

Fig. 13. Shells of species of Leucosyrinx Dall, 1889. A–B. Leucosyrinx verrillii (Dall, 1881), French Guiana, MNHN-IM-2013-56840, SL 25.1 mm. C. L. verrillii, French Guiana, MNHN-IM-2013-56288, SL 31.9 mm (radula seen on Fig. 11C). D–E. Leucosyrinx sp. G. D. Papua New Guinea, MNHN- IM-2009-17089, SL 32.2 mm (radula seen on Fig. 11E). E. Bismarck Sea, MNHN-IM-2013-19689, SL 47.3 mm.F. Leucosyrinx sp. D, Solomon Islands, MNHN-IM-2009-16769, SL 25 mm.G. Leucosyrinx sp. E, Madagascar, MNHN-IM-2009-16897, SL 46.1 mm. H. Leucosyrinx sp. A, Philippines, MNHN- IM-2007-42445, SL 34.1 mm. I. Leucosyrinx sp. B, Solomon Islands, MNHN IM-2009-16764, SL 29.9 mm. J. Leucosyrinx sp. C, Solomon Islands, MNHN-IM-2007-42503, SL 41.2 mm (radula seen on Fig. 11F). K. Leucosyrinx sp. F, Coral Sea, Chesterfield Plateau, MNHN-IM-2007-17846, SL 27.3 mm (radula seen on Fig. 11D). All shells to same scale.